Lubricating and sealing composition of flake copper, powdered lead, graphite, and petroleum vehicle



Patentecl Feb. 27, 1951 LUBRICATING AND I SEALING COMPOSITION OF FLAKECOPPER, 'POWDERED LEAD, GRAPHITE, AND PETROLEUM VEHICLE Henry C.Zweii'el, Inglewood, Calif., assignor to Richfield Oil Corporation, LosAngeles, Calif., a corporation of Delaware No Drawing. ApplicationDecember 2, 1948, Serial No. 63,195

3 Claims. (01. 252-26) My present invention relates to the lubricatingand sealing of threaded joints, pipe joints for instance, and providesan improved method whereby such joints may be effectively sealed againstleakage, yet pressure-welding or galling of the threads prevented. Theinvention also provides an improved thread lubricating and sealingcompound conveniently and effectively used for this purpose.

Th invention is especially applicable to threaded members such as usedon casing, tubing, tool joints, drill pipe and line pipe commonly usedin conjunction with wells, for instance those from which petroleum isproduced, as well as other industrial installations requiring threadedpipe or other conduits for the movement of fluids under variousconditions of temperature and pressure.

Pipe thread lubricating and sealing compounds varying widely in natureand composition have previously been proposed. They have usuallyconsisted of one or more solid constituents such as clay, talc,graphite, powdered zinc, powdered lead, litharge and protein orcellulose solids suspended in some paste-like carrier such aswaterinsoluble greases prepared from calcium or aluminum base soaps orother viscous fluid. Although it appears that soft malleable materialsshould sufilce, they are unsatisfactory with respect to preventing leaksand lubrication. Moreover, most of these materials pack excessively orwork-harden" so that they are diflicult to remove. I have found,however, that finely divided copper in flake form ha significantlysuperior qualities as a pipe thread lubricant. In addition, I have foundthat a combination of copper, powdered lead and amorphous graphite hasunusual properties and value as a lubricating and sealing compoundbecause it protectively lubricates, thereby preventing galling andchafing, while also stopping leakage. I have further found that such' ametallic lubricating medium functions emciently without the presence ofan organic oiliness medium under conditions encountered in threadedmembers.

This application is filed as a continuation in part of my applicationSerial No. 738,744, filed April 1, 1947, now abandoned, in order toamplify the description of my new copper-containing andcopper-lead-graphite lubricants, defined therein, in terms of thedimensions of the copper flakes.

Pipe threads are of various types and design depending upon the servicein which the threaded stock is to be used. Specification tolerances forthe control of lead, taper and pitch of the various types of threads forboth male and female members have been established and are of obviousimportance in reducing leakage. These tolerances, for practicalproduction operations, are such that clearances between mated threadsare sufficiently large toallow seepage of fluids under pressure. Itfrequently occurs that these clearances are not satisfactorily sealed bconventional thread lubricating and sealing compounds. Also, the tapertolerances of two threaded members may be such that the torque requiredfor a tight mating will be largely confined to point contact, resultingin the lubricant being forced from the area and allowing metal-to-metalcontact under high rubbing pressures. This type of lubricant failurefrequently results in pressurewelding or galling of the threads. Andunder the influence of temperature conditions encountered in oil wells,for instance, and other industrial applications, it frequently happensthat the lubricant is adversely affected, resulting in abnormally highbreaking torques being required to separate the threaded connections orthe threads may be frozen so that the application of torques high enoughto break the connection will result in damage to the collar or tubestock. For example, in the production of oil and gas, deep drillingpractices accentuate problems resulting from high pressures, heaviercasing swing loads and higher formation temperatures.

I have discovered that threaded joints may be eifectively lubricated byapplying to the threaded members before mating a composition containingfinely divided copper or a finely divided malleable copper alloy. Thecopper or copper alloy should be in the form of fine flakes or scalesand, with particular advantage, is constituted of particles ranging insize from approximately one micron to at least times larger, in theirlargest dimension, than the maximum combined tolerances of both themating mal and female threads, that is, about 76 microns.

For convenient reference, the term copper will be used herein, and inthe appended claims, to designate either copper or a malleable copperalloy or a mixture of copper and such copper alloy.

Thus I have found that malleable metallic poW- ders or dusts exhibitingphysical forms such as spheres, irregular shapes and heterogeneousforms, as produced in commercial processes, do not provide continuousprotective films. The usual forms of metallic powder have been observedto produce either spotty points of protective material or to have beenpushed or rolled entirely out of the pressure area leaving the thread orbearing surfaces entirely unprotected and subject to seizure or galling.Spots or films of these metallic particles are work hardened and adhereto the thread surfaces. These spots or deposits, resulting from the useof powdered metals in conventional form, especially zinc, lead orcopper, are extremely difficult to remove. If the removal of suchdeposit is not complete, they serve as a base on which metallic buildubecomes very rapid on remaking the joint. This excessive buildup is acause of frozen .Ioints, improper make-up of tubing and casing, andprevents tool Joint threads from making up to a point permitting theshoulders or lands to-face. By contrast, I have determined that copperin the form of very fine flakes or scales will produce, under pressure,an overlapping protective film on the bearing surfaces. The copperflakes, in producing the protective film, form cleavage planes at thepoints of contact between the flakes, thereby substantially assisting inreducing the break away torque required when ordinary metallic powdersare employed. These copper flakes also penetrate and fill chafed orscarred areas on the bearing surface as a protection against furtherdamage, and under suflicient pressure. impregnate the bearing surfacesregardless of the surface hardness of the bearing areas.

Thedimensions of suitable copper flakes are very small, and ordinarilywill be of substantially uniform thickness within the range of 8.0x10-to 19.5xinch. Usually, the flake should not exceed, in its greatestdimension, about 78 microns, or times the maximum combined tolerances ofboth the mating male and female threads as specified by the AmericanPetroleum Institute for threads on oil country tubular stock. Cop indesirable flake form is available commercially, and is produced byseveral methods of manufacture, one of which, for example, is describedin U. 8. Patent No. 2,002,891. 7

The finely divided copper flake of my present invention is used inadmixture with or suspenslon in a carrier, preferably a viscous orsemisolid paste-like carrier having lubricating or rustpreventingcharacteristics, advantageously both. Carriers found particularlysuitable are. those prepared from a petroleum stock and advantageouslycompounded with a rust-preventing lead soap, or other soap, forthickening or impart- 111 suitable body to the petroleum stock. Thepetroleum stock of such carriers usually will comprise from about 30% toabout 85% of the sealing and lubricating compound. In lieu of thepetroleum stock, or in conjunction therewith, I may use an animal orvegetable oil, or both, suitably bodied or thickened by conventionalmeans. Also I may use a viscous solution of a thermoplastic material,for instance, pyroxylin either alone or in conjunction with othercarrier constituents, such as those previously noted. However, themetallic components may be employed with a non-viscous vehicle, likekerosene, there by insuring an even distribution of such constituentsprior to evaporation of the base. Furthermore, the metal components maybe agitated in a container with kerosene, or other similar non-viscousvehicles, and applied with a gun" to the threaded members.

I have determined, however, that these-media do not function as threadlubricants, and accordingly, serve simply as convenient mixing anddistributing aids for the solid ingredients, for it is obvious thatconventional lubricants cannot prevent metal-to-metal contact betweenthe pressure-bearing surface of the mated members when sliding pressuresapproaching the magnitude of 100,000 pounds per square inch areencountered. Indeed, I have found that a joint may be made up using anon-viscous fluid such as benzol as the wetting agent for the solidconstituents. After application of the paste, the benzol is permitted toevaporate leaving a coating of dry solids on the thread The joint makesup and breaks out at normal torques and does not develop thread leakswhen pressure tested. The residual lubricating film on the threadsurfaces, after breaking out the joint, is smooth and oilyv inappearance. and no indication of chafing or galling is detectable.

Although compositions essentially comprising finely flaked copper may beused without the addition of other solid constituents where the primaryconcern isthat of lubrication, the dimensions of the copper flakes aretoo small to function effectively as a damming or sealing agent. Thissealing of threaded'joints against fluid leakage within a normal rangeof temperature may be successfully accomplished by many commerciallyavailable compounds. However, metallic powders, such as lead, zinc,aluminum, tin, etc., when used as such a damming material, exhibit ineach instance some definitely undesirable characteristics.

Powdered lead produces a substantially continuous, and apparently fused,thread of soft malleable metal formed by the compression of the leadpowder between the thread roots and crests of the mating members. Thismetallic thread is an effective sealbut extremely difllcult to removefrom the thread roots. The complete removal of this compressed metallicdeposit is necessary in the case of any threaded joint to be remade, toassure the complete make-up and prevent freezing" or locking of theJoint as a result of overpacking the threads.

Amorphous graphite also forms an impervious dam or plug in the channelbetween the mated thread roots and crests. However, the crushingstrength of graphite is sufiiciently low to result frequently in thedestruction of the seal by the jarring and vibration imposed uponthreaded members during normal handling procedures.

However, I have found that specific combinations of powdered lead andamorphous graphite produce a deposit or dam of completely desirablecharacteristics. The combined powdered lead and amorphous graphitesurprisingly enough produce a seal that is effective at temperaturesranging from ---87 F. to +450 F. and under pressures up to 6000 p. s. i.The physical characteristics of the deposit facilitate easy removal byconventional means normally used in thread cleaning operations.Microscopic examination of the deposit reveals that the deposit iscomposed of substantially individual particles of lead held within amatrix of graphite. The graphite apparently prevents the fusing of thelead particles under the conditions of pressure and temperatureencountered, while the lead seemingly possesses the required stabilityto prevent destruction of the dam under shock or vibration. The graphiteis easily removed by normal cleaning procedures so that the leadparticles are easily washed from the thread roots.

equal proportions of these two constituents have been used withparticular advantage. The ratio 1 of finely divided copper to thecombined proportions of the flaked copper,-amorphous graphite and leadis also subject to considerable variation and may range from not lessthan 5% to as high as 100%, by weight, depending primarily upon theintended use.

The ratio of the combined solids to the carrier and other constituentsmay likewise be varied somewhat depending upon the desired body orstiffness of the resultant compound. About at least 5% of each metallicconstituent, or of the copper flake alone, will produce a satisfactorysealing, lubricant. However, a sealing and lubrieating composition whichis characterized by par ticularly satisfactory performance and economyof manufacture was compounded from the following ingredients in theindicated proportions by weight:

Per cent Flake copper 10.0 Amorphous graphite 10.0 Powdered lead 10.0Viscous petroleum vehicle 65.51 Aluminum stearate soap 4.46Thio-dilauric acid 0.03

The viscous petroleum vehicle is a naphthenic lubricating oil having aSaybolt Universal standard viscosity of 300 to 325 seconds at 100 F.,

while the thio-dilauric acid functions as a rust inhibitor of relativelylow viscosity.

Another compound contemplated by my-present invention which I have foundto be highly effective was compounded from the following ingredients inthe indicated proportions by weight:

Per cent In the foregoing examples the particle size of the amorphousgraphite, powdered lead, and flake copper were within the rangespreviously indicated. The viscous petroleum vehicle employed contained93.63% of a relatively viscous naphthenic petroleum lubricating oilhaving a Saybolt Universal standard viscosity of 300 to 325 seconds at100 F. and 6.37% of an aluminum stearate soap stock.

A thread sealing and lubricating compound exhibiting favorablebrushability at low temperatures and relatively good consistency atelevated temperatures should employ a suitable base material possessingthese properties. A vehicle exhibiting such brushability and suspensioncharacteristics, for example, is one prepared from a light mineral oilof about a 100 second Saybolt Universal standard viscosity at 100 F. andcontaining a small amount of aluminum stearate. The followingcomposition is illustrative of a thread and sealing lubricant exhibitingthese properties:

Per cent Flake copper 16.00 Amorphous graphite 16.00 Powdered lead 16.00Non-viscous petroleum stock 41.59 Thio-dilauric acid 0.03

This compound was not only brushable at F., but showed no separationwhen maintained at +130 F. for a period of seven days. Storage understatic conditions for five months in a temperature range of 60 F. to 100F. showed no indication of separation and centrifugation at an ambienttemperature of approximately 120 F. for an eight-hour period under arelative centrifugal force of 453 showed only a trace of oil separationand no solid separation.

In these compounds the primary function of the amorphous graphite andthe powdered lead is to form a dam between the thread clearances,thereby preventing the flow of fluids along the channel allowed by thethread clearances. The finely divided copper flake likewise serves toform such a dam, but its primary function appears to .be that of forminga protective medium for the thread surfaces, the copper being forcedinto irregularities of the thread surfaces when torque and rubbingpressure are applied, thereby producing' a surface substantially lesssubject to pressure-welding and galling. Thus the carrier or viscouslubricating constituent may be destroyed by heat. or other means,without impairing the damming produced in the thread tolerance channelsor substantially increasing the hazard of galling the thread surface.

I have employed several of my thread sealing and lubricating compoundsto the joints of a pipe string similar to that encountered in actualoperations and compared leakage and torque make-up and break-out resultswith a conventional zinc base lubricant. The pipe string was composed ofnine freshly cut joints fastened with new couplings. The torque make-upor break-out of the joint was determined in footpounds by the use.of amachine employed for such purpose operating at a rotational speed of to3 R. P. M- and capable of applying 7000 horsepower. The leakagecharacteristics of each compound were determined by a water-pressuretesting of the casing, commencing at 1000 p. s. i. and increasing inincrements of 1000 p. s. i. to a final pressure of 6000 p. s. i. Thepressure was held on the joints for two minutes at each increment andfinally, at 6000 p. s. i., for five minutes. The pipe string used as abasis for these comparisons was a seven-inch casing (26 pound-8 threadround-N) section.

Example I To the nine joints was applied a conventional zinc baselubricant comprising essentially by weight 50% of powdered zinc and 50%of an aluminum base grease. This base or carrier was composed ofaluminum stearate and a viscous mineral oil of about a 300 to 325 secondSaybolt Universal standard viscosity at F. The pressure test on thecasing revealed that six of the nine joints leaked at pressures below6000 p. s. 1. within the five-minute test period.

Example II Three of the six joints found to leak in Example I werecovered with a sealing and lubricating compound containing 15% byweight, and in equal proportions, of flake copper, lead and graphite,with a vehicle essentially as described in Example I. The couplings weremade up to 75 7.220 foot pounds and pressure tested to- 6000 Example IIITo the remaining three Joints found to leak in Example I was applied athread sealing and lubricating composition containing by weight 30%, inequal proportions, of the solid components flake copper, lead andgraphite, and a vehicle substantially as indicated in Example I. Thecouplings were made up to 7,220 foot pounds and pressure tested to 8000p. s. i. in which no leaks developed during the two-minute test period.Break-out torques on the joints averaged only 8,783 foot pounds and,upon examination, the lubricant was found to be in good condition andexhibited a smooth, even coating of thread surfaces. The galls andchafing had not increased in any instance, and there was packing andsome healing of the chafing and scars on these surfaces to which thiscomposition was applied.

In addition, I- have compared the make-up torque, break-out torque andleakage characteristics of a sealing lubricant containing about 22% ofeach metallic component, as hereinbefore described, with a conventionalzinc base compound. The three types of tubular stock used were a 7-inchcasing (26 1b., 8 thread round), a 2 /A-inch external upset tubing (6.50

lb., 8 thread round) and a 2-inch external upset,

tubing (4.70 1b., 8 thread round). The high temperature test wasconducted by the application to the stock of 30-minute elevatedtemperatures of 406 E, 410 F. and 385 F., respectively, while thepressures were varied up to 6000 pounds per square inch in the casingsand 3500 pounds per square inch in the tubings.

Example IV Increase in Breakout Torque over make-up Torque, per centConventional mung 'lubular stock 221cc lubricant I! ated Heated heated aheated Per emf- Per Peril :5? Per 7-inch casing +43 l d-inch tubing +82+384 +26 +109 2-inch tubing +18 +179 20 +65 Thread leaks developed, percent of total joints leaking Conventional New mung I Tubular stock zincbase lubricant lubricant Heated Heated heated heated Per cent Per egg!Per cegt Per cen 7-inch casing 28 2}-inch tubing 0 100 0 0 2-inch tubing0 0 0 0 My method of sealing and lubricating threaded Joints and thecompound effective to this end may be used with satisfactory results onthe threaded members of bill: pressure-lamb temperature steam pipes asused in refineries or boiler gaskets, bolts and studs, engines in theautomotive industry, aircraft engines, water and acid pipes and on tubesand piping that are bent in different shapes and sizes. In particular,it is very effective in preventing the leakage of fluids through thethreaded Joints in the casing and tubing strings used in the productionof petroleum oils and gases, thereby avoiding the loss of easingpressure, the infiltration of water and escape of product.Deeper'drllling practices characteristic of present day petroleumproduction has accentuated the need for such a sealing lubricant as Ihave described because of heavier string loads and higher formationtemperature and pressures encountered at such lower subterranean levels.

It will be understood that the reference herein, and in the appendedclaims, to the rust preventive lead soap is intended to includecompounds of lead and animal or vegetable fats, fatty acids, or fattyacid derivatives, as well as certain petroleum derivatives, particularlyoxidized petroleum, and that reference to other metallic soaps isintended to include compounds of metals other than lead, notably sodiumor calcium, and animal or vegetable fats, or fatty acids.

I claim:

1. A thread sealing and lubricating compound comprising essentiallyfinely-divided copper in fiake form of particle size within the range offrom one micron to about 76 microns, powdered lead, amorphous graphiteand a petroleum vehicle, the petroleum vehicle comprising from about 30%to about of the compound and forming a medium in which thefinely-divided copper, the powdered lead and the amorphous graphite aresuspended, the lead being present in amount from about one-third part tothree parts by weight to each part by weight of the graphite, and theproportion of the finely-divided copper to the combined amount of thecopper, lead and graphite being in the range of from 5 to 2. A threadsealing and lubricating compound compounded from the followingingredients in proportion by weight, substantially as indicated:

Per cent Flake copper 10.0 Amorphous graphite 10.0 Powdered lead 10.0Viscous petroleum vehicle 65.51 Aluminum stearate soap 4.46Thio-dilauric acid 0.03

the particle size of the fiake copper being in the range of from onemicron to about 16 microns.

3. A thread sealing and lubricating compound compounded from thefollowing ingredients in proportion by weight, substantially asindicated:

the flake copper being of a particle size within the range of from onemicron to about 76 microns, and the other metallic soap being a metallicsoap from the class consisting of sodium soaps and calcium soaps.

HENRY C. ZWEII'EL.

(References on following page) The toll owing references are of recordin the flleofthispatent: 2,205,990

UNITED STATES PATENTS 5 Number Name I Date 7 1358.598 mull May 13, 193012:? 6

Name Date Smith Dec. 22. 1936 'Campbell Dec. 12, 1939 Nelson et a1. June25, 1940 FOREIGN PATENTS Country Date Great Brltaip l Nov. 15, 1923

1. A THREAD SEALING AND LUBRICATING COMPOUND COMPRISING ESSENTIALLYFINELY-DIVIDED COPPER IN FLAKE FORM OF PARTICLE SIZE WITHIN THE RANGE OFFROM ONE MICRON TO ABOUT 76 MICRONS, POWERED LEAD, AMORPHOUS GRAPHITEAND A PETROLEUM VEHICLE, THE PETROLEUM VEHICLE COMPRISING FROM ABOUT 30%TO ABOUT 85% OF THE COMPOUND AND FORMING A MEDIUM IN WHICH THEFINELY-DIVIDED COPPER, THE POWDERED LEAD AND THE AMORPHOUS GRAPHITE ARESUSPENDED, THE LEAD BEING PRESENT IN AMOUNT FROM ABOUT ONE-THIRD PART TOTHREE PARTS BY WEIGHT TO EACH PART BY WEIGHT OF THE GRAPHITE, AND THEPROPORTION OF THE FINELY-DIVIDED COPPER TO THE COMBINED AMOUNT OF THECOPPER, LEAD AND GRAPHITE BEING IN THE RANGE OF FROM 5 TO 100%.